The present invention relates to a water purification/sterilization method and its device to be used, for example, with swimming pools, baths, 24-hour public baths, ponds, farming tanks, AC water, waste water from car wash services, and waste water from combined treatments.
In a related field, water from, for example, a swimming pool, 24-hour bath, farming tank, or AC water is relatively well controlled for purification. In general, a swimming pool is purified and sterilized by employing sand filtration and the introduction of chlorine, and a 24-hour bath is purified through filtration and a biological treatment.
In general for a swimming pool, a coagulation treatment/sand filtration, and purification and sterilization through the introduction of chlorine are carried out. When the purification does not remain adequate for the number of people in the pool, the water gets foul and the clarity of the water becomes 7 to 8 m in the late afternoon, where it was 20 m or more in the morning.
When the water is foul, the number of bacteria increases and it is a sanitary problem. Therefore, the amount of chlorine introduced is increased. Consequently, problems are generated such as a chlorine smell remains and people are often irritated by the chlorine, such as by eye irritations, skin problem for their aims and legs or their hair is damaged.
In addition, a purification method using a coagulation treatment/sand filtration requires a frequent reverse filtration of the sand and consequently increased water consumption.
24-hour baths were popular and there were 1.2 million of them at the peak, however, an investigation carried out from the end of 1996 to February 1997 revealed that legionella bacteria were found in a wide range of water from a 24-hour bath and this created a social problem. It was discovered that the generally used biological treatment was actually providing a desirable environment for the propagation of legionella bacteria.
The present inventors have submitted the following patent applications that are related to a purification/sterilization method of water employing electrolysis and its device for water such as swimming pool, baths, 24-hour baths, farming tanks, ponds, AC water, wastewater from car washes, and wastewater from combined treatments.
Japanese Patent Laid-open Publication Nos. H06-296968/1994, xe2x80x9cWater purification device for a swimming pool and bath,xe2x80x9d H08-089969/1996 xe2x80x9cWater purification method and its device,xe2x80x9d H11-128942/1999 xe2x80x9cWater quality purification method and its mechanism,xe2x80x9d H11-188364/1999 xe2x80x9cElectrolyzing device,xe2x80x9d H11-207349/1999 xe2x80x9cWater quality purification mechanism,xe2x80x9d H11-207350/1999 xe2x80x9cWater quality purification mechanism,xe2x80x9d H11-207353/1999 xe2x80x9cWater or waste water purification method and its device,xe2x80x9d 2000-046793 xe2x80x9cWater foulness evaluation systemxe2x80x9d and 2000-140899 xe2x80x9cCombined treatment purification system and its combined treatment purification device.xe2x80x9d
Of the patents disclosed above, the water purification/sterilization of swimming pools and baths through electrolysis was made possible in accordance with H06-296968 and H08-089969. As the anode of the electrolyzing device, a platinum-plated titanium electrode displaying the strongest corrosion resistance was used, however, when there were high loads, the electrolytic voltage became abnormally high in a short period of time. Thus, in accordance with the H11-188364 xe2x80x9cElectrolyzing devicexe2x80x9d, a ferrite anode through a new terminal bonding method was employed and consequently, 3 to 5 times longer endurance performance under the same conditions, compared to the platinum-plated titanium electrode, was achieved.
Nonetheless, there is a problem such that when the current value is increased in order to achieve a higher purification/sterilization effect, the terminal portion is heated. In addition, in order for easy installation in a compact place such as an existing bathtub or aquarium water, a purification/sterilization device that employs an electrolyzing device that is compact, durable without failure and safe, is desired. At the anode, halogen ion discharges negative electricity and the halogen that is deposited at the same time, due to a strong acid such as hydrochloride that is generated by hydrolysis, creates a low PH. Because it creates a strong acidic environment, an anode is required that has a high corrosion-proof electrode. Therefore, from past performance, a ferrite is selected, and a ferrite round rod or tube with a long hole in the direction of the center axis of the rod or tube or in the longitudinal direction is employed as an anode 1 in the center. Unlike a regular metal electrode, ferrite does not have a high electric conductivity, and because it is ceramic it is therefore hard and brittle, making it difficult to bond the terminal with a prior art such as welding. The present inventors have invented an electrolyzing device that resolves this problem, and have submitted a patent application published as 2000-168578. Nevertheless, the main objectives of this invention were to electrolyze a solution in which a high concentration of halogen ion is dissolved in regular tap water and then to create sterilized water with a high concentration of the remaining hydrochloride.
Water from a swimming pool, bath, pond, 24-hour bath, farming tank, or AC water has a low electric conductivity of 200 to 900 xcexcS/cm. In addition, in order to purify foul water, a large electric current has to flow per electrode area. When adding, for example, sodium chloride increases the electric conductivity it corrodes the hardware of the swimming pool or bath, and it is not appropriate for freshwater farming. Furthermore, when a large amount of water is electrolyzed continuously for a long period of time, it creates a problem such as breakage occurs due to the deterioration and deformation of the electrode and the electrolytic cell due to the overheating of the electrode from the increase in electrolytic voltage.
The application of an electrolyzing device, employing a ferrite electrode for an anode, to water purification/sterilization for swimming pools, baths, ponds, 24-hour baths, farming tanks, and AC water has been known to be a superior purification/sterilization method, having a high purification/sterilization effect without harmful effects on humans and other organisms. However, for water with low electric conductivity, the electrolyzing device of the prior art has a problem with its durability.
The objectives of the present invention are to provide a compact foul water purification/sterilization method and its device employing an electrolyzing device with high efficiency of electrolysis wherein even under continuous operation for a long period of time in water with a low electric conductivity, the deterioration or breakage of the electrode or thermal deformation of the plastic case of the electrolyzing device does not occur.
In order to resolve the above-mentioned problem, the present invention employs the following means. In order to have a compact and durable structure in which there will be no leakage from the electrolyzing device, even after long-term use, a multiplicity of barrel-shaped anodes and cathodes are alternately arranged in a concentric manner in layers with intervals of 1.1 to 9 mm between electrodes, and in between the electrodes, water comprising a halogen ion is poured to be electrolyzed and sterilized.
With electrolyzing device 1 of the present invention, anodes 3 comprise ferrite pipes or rods, or conductive metal pipes or rods with a thermal sprayed ferrite film. The cathodes 4 comprise a conductive metal pipe. The electrolyzing device 1 is structured such that anodes 3 and cathodes 4 are alternately arranged in a concentric manner in layers with intervals of 1.1 to 9 mm between electrodes. Then, in between the electrodes, water comprising an electrolyte is poured and said water is electrolyzed. Anodes 3 are ferrite rods with a long hole along the central axis direction (longitudinal direction), or a ferrite pipe, in which a soft conductive metal with a low melting point of 6 or mercury is filled in the hole in advance. Then, the rod-shaped conductive terminal 5 is inserted therein. External to anodes 3, conductive corrosion resistance metal pipes are arranged in a concentric manner in layers as cathodes 4.
One or multiple electrolyzing devices 1 that are structured as above is/are stored at a right angle in a mesh or conductive protective case 16 having holes 17. Then they are directly installed by being immersed in the water of a bathtub, swimming pool, or farming tank that is the subject to be purified/sterilized. Alternatively, one or more of the electrolyzing devices 1 are installed in the external circulation line of the electrolyzing device. Then, in between the electrodes, used foul water that comprises a halogen ion, or foul water that is newly added with a solution comprising a halogen ion is supplied, and electrolysis can be carried out while the designated electric conductivity is maintained. Then, the purified/sterilized water is drained out from the container. In this case, when the electric conductivity of the subject water is low, it is acceptable for a solution of bromine ion, chlorine ion, or a mixture of bromine ion and chlorine ion, as a halogen ion to be added and the water purification/sterilization can be carried out while the designated electric conductivity is maintained.
The water purification/sterilization device of the present invention is to be directly installed by immersing it in water tanks, such as the water of a swimming pool, bathtub, farming tank, AC system, or installed in a balancing tank or water treatment tank of a water circulation line. Therefore, it is acceptable that it comprises a mesh or lattice-shaped corrosive resistant conductive metal protective case that allows grounding, one set or multiple sets of electrolyzing devices 1 in the case, a power source installed outside the tank, an operation control device, and a tank and pump for supplying the electrolyte. It is also acceptable that in the water circulation line, the electrolyzing device is installed upstream from the filter, so that the water purified by an electrolytic treatment, which contains hypohalogenous acid with a high oxidation power, created by electrolysis, penetrates the filter and circulates. In addition, when the filter is back washed regularly for cleaning purposes, a reverse switching valve is switched so that the water containing hypohalogenous acid with a high oxidation power reverse flows through the filter with a back wash line, and the water purification/sterilization is carried out. In this case, it is possible that during a long-term electrolysis, an electrolyzing device can be immersed in a solution of an inorganic acid such as hydrochloride, or an organic acid such as acetic acid, at given intervals of time, in order to remove deposits on the cathode of, for example, metal hydroxides. Moreover, it is acceptable that the purification/sterilization device is installed midway in the water circulation line, and it is structured such that there is: a compact water treatment tank in which an electrolyzed device is immersed in a purification/sterilization device; a supply tank, for a solution of an inorganic acid such as hydrochloric acid or an organic acid such as acetic acid, which is installed with a connection to said water treatment tank and a metering pump; a drainage means that is installed at the bottom of said water treatment tank; a power source and a control device that controls the operations, the control of the electrolysis, and the supply of an inorganic acid such as hydrochloride or an organic acid such as acetic acid, and drainage.